Thrust bearings are used in tools, machines, and components to, at least predominately, bear axial load. Thermally stable polycrystalline diamond (TSP), either supported or unsupported by tungsten carbide, and polycrystalline diamond compact (PDC or PCD) have been considered as contraindicated for use in the machining of diamond reactive materials, including ferrous metals, and other metals, metal alloys, composites, hard facings, coatings, or platings that contain more than trace amounts of diamond catalyst or solvent elements including cobalt, nickel, ruthenium, rhodium, palladium, chromium, manganese, copper, titanium, or tantalum. Further, this prior contraindication of the use of polycrystalline diamond extends to so called “superalloys”, including iron-based, cobalt-based and nickel-based superalloys containing more than trace amounts of diamond catalyst or solvent elements. The surface speeds typically used in machining of such materials typically ranges from about 0.2 m/s to about 5 m/s. Although these surface speeds are not particularly high, the load and attendant temperature generated, such as at a cutting tip, often exceeds the graphitization temperature of diamond (i.e., about 700° C. or 973.15 K), which can, in the presence of diamond catalyst or solvent elements, lead to rapid wear and failure of components. Without being bound by theory, the specific failure mechanism is believed to result from the chemical interaction of the carbon bearing diamond with the carbon attracting material that is being machined. An exemplary reference concerning the contraindication of polycrystalline diamond for diamond catalyst or solvent containing metal or alloy machining is U.S. Pat. No. 3,745,623, which is incorporated herein by reference in its entirety. The contraindication of polycrystalline diamond for machining diamond catalyst or diamond solvent containing materials has long caused the avoidance of the use of polycrystalline diamond in all contacting applications with such materials.
Over time, as polycrystalline diamond bearings were developed, bearing makers either matched the polycrystalline diamond bearing surfaces with non-ferrous, so called superhard materials or, much more commonly, with tightly facing complementary polycrystalline diamond surfaces. FIG. 1 depicts a partial cutaway view of thrust bearing 100, having a polycrystalline diamond to polycrystalline diamond interface. As used herein, “superhard” materials are defined as materials at least as hard as tungsten carbide (e.g., cemented tungsten carbide or tungsten carbide tiles) or harder, including, but not limited to, tungsten carbide, infiltrated tungsten carbide matrix, silicon carbide, silicon nitride, cubic boron nitride, and polycrystalline diamond. As would be understood by one skilled in the art, hardness may be determined using the Brinell scale, such as in accordance with ASTM E10-14. Exemplary references concerning polycrystalline diamond thrust bearings are U.S. Pat. No. 4,468,138 to Nagel; U.S. Pat. No. 4,560,014 to Geczy; U.S. Pat. No. 9,702,401 to Gonzalez; and U.S. Defensive Publication T102,90 to Offenbacher, the entireties of each of which are incorporated herein by reference.
High performance polycrystalline diamond thrust bearings designed particularly for harsh environments, such as downhole drilling and pumping, or wind turbine energy units, typically utilize sliding, mated, overlapping polycrystalline diamond elements. This requires a large number of polycrystalline diamond elements, each in exacting flat engagement with an opposing set of polycrystalline diamond elements. The polycrystalline diamond elements must be mounted at exactly prescribed heights or exposures to insure mated sliding engagement. The goal in the prior art is full face contact of the polycrystalline diamond elements on both faces as bearing areas. Failures in alignment and/or exposure are likely to produce point loading, uneven load sharing or “edge clashing” as the polycrystalline diamond elements rotate against each other producing fractured elements and, ultimately, bearing failure. Polycrystalline diamond is more brittle and prone to impact damage than diamond reactive material (defined herein below).
Table 1, below, sets for a summary of coefficients of friction for various materials, including polished polycrystalline diamond, in both a dry, static state and a lubricated, static state, where the “first material” is the material that is moved relative to the “second material” to determine the CoF of the first material.
TABLE 1*FirstSecondDryLubricatedMaterialMaterialStaticStaticHard SteelHard Steel0.780.05-0.11TungstenTungsten0.2-0.250.12CarbideCarbideDiamondMetal0.1-0.150.1DiamondDiamond0.10.05-0.1Polished PDCPolished PDCEstimatedEstimated0.08-10.05-0.08Polished PDCHard SteelEstimatedEstimated0.08-0.120.08-0.1*References include Machinery's Handbook; Sexton T N, Cooley C H. Polycrystalline diamond thrust bearings for down-hole oil and gas drilling tools. Wear 2009; 267: 1041-5.
Additional significant references that inform the background of the technology of this application are from the International Journal of Machine Tools & Manufacture 46 and 47 titled “Polishing of polycrystalline diamond by the technique of dynamic friction, part 1: Prediction of the interface temperature rise” and “Part 2, Material removal mechanism” 2005 and 2006. These references report on the dynamic friction polishing of PDC faces utilizing dry sliding contact under load with a carbon attractive steel disk. Key findings in these references indicate that polishing rate is more sensitive to sliding rate than load and that the rate of thermo-chemical reaction between the steel disk and the diamond surface reduces significantly as the surface finish of the diamond surface improves. The authors reference Iwai, Manabu & Uematsu, T & Suzuki, K & Yasunaga, N. (2001). “High efficiency polishing of PCD with rotating metal disc.” Proc. of ISAAT2001.231-238. which concludes that the thermo-chemical reaction between the steel disk and the PDC face does not occur at sliding speeds below 10.5 m/s at a pressure of 27 MPa. These references are incorporated herein by reference, as if set out in full. It should be emphasized that the above numerical values are based on dry running in air. Clearly, if running in a liquid cooled, lubricated environment, higher speeds and loads can be attained without commencing the thermo-chemical reaction. Also, of note is the lower thermo-chemical response of a polycrystalline diamond face that has been polished. Copper and titanium were not typically listed in the early General Electric documentation on diamond synthesis but have been added later. Relevant references include “Diamond Synthesis from Graphite in the Presence of Water and SiO2”; Dobrzhinetskaya and Green, II International Geology Review Vol. 49, 2007 and “Non-metallic catalysts for diamond synthesis under high pressure and high temperature”, Sun et al, Science in China August 1999.